Parkinson's Disease

Association France-Parkinson

Parkinson's disease is a slow progressive neurodegenerative disease of the central nervous system, and it is the fourth most frequent degenerative disease to affect the elderly. About 1% of individuals aged 65 and over are affected regardless of their gender. The aetiology of Parkinson's disease is unknown. It is characterized by a combination of neurological signs and its clinical picture is presented with diverse signs and symptoms. Treatments have positively changed the usual prognosis of survival, but the disease is often responsible for significant disabilities, although its progression is highly variable.

What is Parkinson's disease?

Parkinson's disease is a neurologic condition mostly associated with progressive degeneration of the dopaminergic nigrostriatal system (neural pathways that use dopamine), and the locus of interest are the substantia niagra and striate body.

First described in 1817 by James Parkinson as 'paralysis agitans', Parkinson's disease is characterized by a triad of symptoms (combination of 3 signs) which are, resting tremor; dyskinesia (delayed initiation and slowness of movements); and muscular rigidity. These are the hallmarks of an extrapyramidal lesion or parkinsonian syndrome.

What are the clinical signs?

The average age of onset is 57 years old, but the disease occurs before age 40 in less than 10% of cases. Although Parkinson's disease is easy to diagnose once it has fully set in, it is difficult during the initial phases because the symptoms are very mild and discrete in nature. The diagnosis is made by simple clinical examination, preceded by medical history taking, and generally does not require any other test.

Diagnostic features of early Parkinson's disease

Four features must be present: progressive akinesia; absence of pyramidal signs, presence of cerebellar, vestibular, or sensory impairments, dementia, no response to neuroleptic drugs during the previous 12 months; positive response to Levo Dopa therapy.

Additionally, at least one of the following features: resting tremor; muscular rigidity; assymetric of symptoms.

Note: More than a third of individuals diagnosed with parkinson's disease do not experience tremor. Therefore the onset of tremor in the elderly should not be associated with Parkinson's disease. The constantly changing nature of the symptoms is one of the features of this disease. In 35 to 50% of cases, it is accompanied with depression.

What is the cause?

The cause of lesions and biochemical mechanisms observed in Parkinson's disease remains unknown. The current assumption is the probable interaction between environmental factors and endogenous mechanisms (internal) along with ageing in genetically predisposed individuals.

Lesions and mechanisms of Parkinson's disease

Lesions can be described as neuronal loss (reduction in the number of neurons) in the brainstem's pigmented nuclei, especially in the substantia nigra. Under microscopic examination, abnormal accumulations can be observed within the neuronal cell (Lewy bodies). At the neurochemical level, progressive degeneration of dopaminergic pathways (producing dopamine, which transmits signals from a neuron to another) can be observed with impaired synaptic receptors (junction between neurons).

The substantia nigra and other relay centers of the extrapyramidal motor pathways.

Disease progression

Before the discovery of levodopa or L-Dopa (1969), the spontaneous progression of the disease resulted in a rapid confinement to bed due to infectious complications, especially pulmonary infections. Treatments currently in use ensure a normal life, but these drugs have developed a group of symptoms that were unknown to date: the 'levodopa-treated Parkinson's disease'. The symptoms are as follows:

Note: this progression is avoidable: many affected individuals experience a stable phase during many years without aggravation, and enjoy variable but significant motor capability.

What are the suggested treatments and management strategies?

Substitutive and symptomatic therapies are used, but never etiologic therapies. The latter do not have any effect on the disease progression.

The purpose of the treatment is to supply the missing dopamine to neurons and to restore the dopamine/acetylcholine balance using L. Dopa and other medications. The major issue of all these treatments is their decreasing efficiency after a few years, which requires, in some cases surgical intervention, such as the electrical stimulation of the thalamic and subthalamic area, which attenuates tremors and freezing phenomena. Gene therapy has given rise to great hope for the long-term future.

Finally, physiotherapy complements the medical treatment, which is critical in Parkinson's disease. It must be introduced as early as possible and as soon as the diagnosis is confirmed, and be monitored regularly throughout the period of illness.

Living with Parkinson's disease

Complying with certain instructions enhance quality of daily living and the efficiency of treatments: